Synthesize LHRH analogs in 10 mg quantities. Synthesize related LHRH antagonists. Provide evidence of homogeneity of the analogs by paper or thin layer electrophoresis, thin layer chromatography, HPLC, elution profile, and amino acid analysis. Determine the antagonist or agonist activity of these analogs using in vitro inhibition of LHRH mediated secretion of gonadotropins by pituitary cell cultures. Determine the antiovulatory activity of the inhibitors in rats. Determine the long-acting activity of selected peptides. Conduct radioligant membrane binding studies. Make those analogs with significant biological activity available to the Project Officer.